Spirobranchus minutus Rioja 1941

Spirobranchus minutus (Rioja, 1941b)

(Figures 8, 13 H)

Pomatoceros minutus Rioja, 1941b: 734 –738, pl. 9, Figs 15–26. Type locality: Acapulco, Guerrero, hydrocaulus of Pennaria Goldfuss (type specimens lost).

Pomatoceros minutus.— Rioja 1942: 130 –132, Figs 15–21 (Mazatlán, Sinaloa, and Río Mayo, Sonora, 15 m, on shell of Pteria Scopoli, as Avicula Bruguière); Rioja 1946: 201 –202 (Veracruz, on algae entangled in fisherman nets); Rioja 1947a: 215 (Mapahui, Topolobampo and Navachiste, Sinaloa); Berkeley & Berkeley 1958: 405 (Abreojos Point, Baja California Sur; floating seaweed); Weisbord, 1964: 161 –164, pl. 21, Figs 4–5, pl. 22, Figs 3–4 (recent, Playa Grande Yachting Club and Higuerote beaches, northern Venezuela, on several mollusk shells; and fossil, same as Serpulorbis catella); Zibrowius 1970: 15 –16, pl. 3, Figs 11 –15 (São Sebastião and Ubatuba, Brazil, 6–15 m, on rocks, madrepores and gorgonians); Shepherd 1972: 5 (La Paz Bay, Baja California Sur; epifauna on Pinctada mazatlanica); Salazar-Vallejo 1989b: 200 (Mexican coasts, checklist); Bastida-Zavala 1993: 35 (Caimancito Beach, Baja California Sur); Salazar-Vallejo & Londoño-Mesa 2004: 55 (Tropical Eastern Pacific, checklist); Lewis et al. 2006: 669 (ten Hove identified specimens from the tall ship “Gorch Fock” in Sydney, Australia); Bastida-Zavala 2008: 31–33, Figs 7 H–M (Hawaii, Baja California Sur, Guerrero, Oaxaca, Costa Rica and Perú; intertidal to 17 m); Hernández-Alcántara et al. 2008: 49 (mentioned only); Bastida-Zavala 2009: 538, Figs 3 O, 5M (identification key for Tropical America); ten Hove & Kupriyanova 2009: 76 (worldwide serpulid checklist); Villalobos-Guerrero et al. 2014: 107 (Sinaloa, checklist).

Serpulorbis catella Weisbord, 1962: 156 –157, pl. 13, Figs 17–18 (fossil, type locality: Lower Mare and Abisinia formations, Venezuelan Pliocene and Pleistocene; on pelecypod shell).

Pomatoceros caeruleus (not Schmarda, 1861).— Rioja 1963: 220 (Mazatlán, Sinaloa; Guaymas, Sonora; and Zihuatanejo, Guerrero; on algae and mollusc shells); Salazar-Vallejo 1989b: 200 (Mexican coasts, checklist).

Placostegus sp.— Bastida-Zavala 1995: 25 (Cabo Pulmo Reef, Baja California Sur, on coral; 4–17 m).

Pomatoleios crosslandi (not Pixell, 1913).— Bastida-Zavala 1995: 25 (Cabo Pulmo Reef, Baja California Sur, on coral; 17 m).

Pomatoceros cf. minutus.— Bastida-Zavala & Salazar-Vallejo 2000a: 814 –815, Figs 5 a–f (Cazones, Veracruz, and IMCA IV, sta. 41, Campeche; 42 m).

Spirobranchus minutus.— Pillai 2009: 146 –148 (new combination, synonymy of the genera Pomatoceros Philippi and Pomatoleios Pixell with Spirobranchus); Bastida-Zavala et al. 2013: 349 (Oaxaca, checklist).

Material examined. 106 specimens.

Baja California Sur: UANL 7901 (Marina Cantamar, Pichilingue, La Paz, 24°16.173’N, 110°19.839’W, April 22, 2010, coll. JAL).

Michoacán: UMAR-Poly 810, 6 spec. (Faro de Bucerías, on sabellariid tubes, December 21, 1996, coll. SGM); UMAR-Poly 811, 9 spec. (Caleta de Campos, on sabellariid tubes, December 17, 1994, coll. RBZ).

Guerrero: UMAR-POLY 812 (La Ropa Beach, Zihuatanejo, on rock with algae, September 20, 2007, coll. SGM et al.); UMAR-POLY 813, 6 spec. (Manzanillo Beach, Zihuatanejo, on exposed algae, September 21, 2007, coll. SGM et al.); UMAR-POLY 814, 2 spec. (Morro del Cerro Colorado, Nov 30, 2010, coll. SGG); UMAR-Poly 815 (La Roqueta Island, Acapulco, on sabellariid tubes, May 26, 2000, coll. RBZ); UMAR-Poly 816 (Cantiles, Acapulco, on oysters, 8 m, May 26, 2000, coll. AM).

Oaxaca: UMAR-POLY 817, 14 spec. (Corralero Lagoon, on mangrove, December 7, 2006, coll. RBZ); UMAR-POLY 818-OH, 6 spec., 3 donated to Elena Kupriyanova (Agua Blanca Beach, high tide, on sabellariid tubes, September 9, 2010, coll. BMD); UMAR-POLY 819, 30 spec. (Panteón Beach, intertidal, on rocks, June 12, 2012, coll. ERR & MJC); UMAR-POLY 820, 2 spec. (Puerto Ángel, on pier, May 20, 2007); UMAR-POLY 821 (Estacahuite Beach, intertidal, on rocks, June 2, 2012, coll. AVB & MTM); UMAR-POLY 822, 2 spec. (Marina Chahué, Huatulco, on rocks, May 22, 2000, coll. RBZ); UMAR-POLY 823, 7 spec. (same, on mollusc, May 22, 2000, coll. RBZ); UMAR-POLY 824, 3 spec. (El Arrocito Beach, Huatulco, July 4, 2007, coll. FCC & SRH); UMAR-POLY 825, 7 spec. (La Ventosa pier, Salina Cruz, May 21, 2000, coll. SSV et al.); UMAR-Poly 826, 2 spec. (Laguna Inferior, San Dionisio del Mar, 16°18’8”N, 94°44’56”W, 0.5 m, salinity= 30.77 PSU, August 30, 2014, coll. CPR); UMAR-POLY 827, 5 spec. (from Oaxaca, no more data).

Habitat. Intertidal to subtidal (42 m, Bastida-Zavala & Salazar-Vallejo 2000a). Some specimens were collected from anthropogenic substrates in marinas (from La Paz, Baja California Sur, and from Huatulco and Salina Cruz, Oaxaca), as hull fouling, with salinity range of 30–36 PSU; also in brackish-water lagoons on mangrove roots; in marine water on rock bottoms, dead coral Pocillopora verrucosa, sabellariid colonies, hydrozoa Pennaria, and on Pteria and oysters shells (Bastida-Zavala 2008). Fouling species.

Distribution. Native in Tropical Pacific America. Baja California Sur (México) to Perú (Rioja 1941b; Rioja 1942; Bastida-Zavala 1993). It also was recorded from Brazil (Zibrowius 1970), the Gulf of Mexico (Rioja 1946; Bastida-Zavala & Salazar-Vallejo 2000a), Sydney (Lewis et al. 2006) and Hawaii (Bastida-Zavala 2008), where it should be considered to be an exotic species.

Remarks. Spirobranchus minutus was found both on natural and anthropogenic substrates. It is a fouling species with potential to be introduced to other tropical regions by ships. We suspect that its presence in the Tropical Western Atlantic represent an historical introduction as fouling via ships, because it is recorded from few sites, some related to ports or fouling plates: Veracruz Port (Rioja 1946), Cazones, Veracruz (river mouth, collected in 1981), Campeche Bank (oil platforms, collected in 1989), São Sebastião and Ubatuba, Brazil (collected in 1961– 1962) (Zibrowius 1970; Bastida-Zavala & Salazar-Vallejo 2000a) and the northern of Gulf of Mexico (from fouling plates in ports, collected between 1999-2005, Bastida-Zavala et al., unpublished data).

An alternative hypothesis is that the species has a true Amphiamerican distribution, considering the Recent and fossil (Pliocene and Pleistocene) records of Spirobranchus minutus from northern Venezuela (Weisbord 1962; 1964), the species may have had a free genetic flux between the eastern Pacific and Caribbean populations when the Isthmus of Panamá had not yet been formed (3.5 million years ago). Whether or not populations of both Tropical American coasts are the same can only be decided by a DNA analysis.

In 1990, ten Hove identified several adult specimens of Spirobranchus minutus (co-occurring with Hydroides brachyacantha), scraped from the tall ship “Gorch Fock” that arrived in Sydney Harbor after an almost three weeks stay in Acapulco, Guerrero (in: Lewis et al. 2006: 669). Bastida-Zavala (2008) recorded this species in Hawaii from the hull of a sailboat too, after of a four-month voyage from San Francisco, Los Angeles, México to Hilo and Honolulu, Hawaii.